Most people have pictures of their children, pets and partners on their iPhone. Not Donall McCusker: his gallery includes soldiers hefting large guns, profile shots of Arabic-looking men and perfectly timed snaps of explosions – the kind of thing that would immediately lead to his detention if spotted by airport security staff.

It might take him some time to convince them of his innocence: he was brought up in Belfast and still has a distinct accent which, combined with the photos, might start alarm bells ringing.

But McCusker has the best reason in the world to be carrying these photos: he was co-producer on the war film The Hurt Locker, which picked up six Academy Awards this year, and his photos are all of people and events that appear on screen.

The film follows a US army explosive ordinance disposal team in the last few weeks of its rotation in Baghdad.

It was filmed in Jordan and used Iraqi refugees as extras to increase authenticity. McCusker negotiated the use of the Jordanian army and its equipment, and oversaw the staging of bombs going off.

"It's just petrol and black powder," he says. "Nothing gets damaged. We blew that building up (he points to a picture of a school) four times."

Google the term co-producer and you'll be given several definitions. In McCusker's case, it means a line producer or production manager; he is responsible for all the logistical planning and spending for the film. He recruits (not to be confused with casting) most members of the crew apart from the director and producer, and will negotiate the cost of every aspect of filming. After the producer and director have said what they want, he makes it happen.

"I'm responsible for the investors' money, for delivering the film to the producers for the agreed budget," he says. "As senior management I will typically spend £2m to £4m in as many months and be responsible for hiring 200 people. I try to squeeze as much as I can out of the money. I'm also responsible for prioritising, because everybody wants everything at once."

For The Hurt Locker, his role ranged from negotiating the use of a whole town – Madaba – for a week, with its governor, asking Jordan's army if he could borrow their tanks, trucks and planes, through to working out the pay for extras. "You can't rip people off. But if you pay too much, you'll end up closing down the Jordanian film industry – it will get too expensive."

He settled on £20 a day, "but that's good money for a local rate of pay".

I wonder if McCusker finds it frustrating not to be involved on the creative side, but he insists not: eking out a film's budget inevitably means he is involved in some creative decisions.

"Officially my creative involvement is not much," he points out, "but in practice I'll make a lot of suggestions that affect what appears on screen. In my last film there was a scene which involved a character getting off a bus and crossing the street. I said, 'Do you know how much it costs to hire a bus? Can't he ride a bike and get off that? And that's what we ended up doing."

At university McCusker studied for an electrical engineering degree, but soon realised that wasn't for him and instead started work as a runner at Granada TV on the series Families. That led to him producing a TV movie screened in Northern Ireland.

Many people find the only way they can get into the film industry is by working for free, something McCusker wants to change: "We're trying to stop that because it means people from low-income backgrounds can't afford to get in, but it's difficult when there's 100 people for every job," he says.

Sheer persistence is the main attribute needed to crack the industry, he says. "You almost need to be unemployable at everything else, because if you can do something else, you will probably give in and do it when you're struggling to get into films."

McCusker studied production management at the National Film and Television School (NFTS) but is sceptical about the value of some film courses in helping to start people's careers. "Many training courses don't particularly help because it's not a career that you get a qualification in and then do it," he says. "To establish a career you need to develop a network of contacts within the industry. It's a people business and making friends is as much a part of it as working hard."

However the NFTS course enabled him to jump several rungs of the ladder, starting work in TV as a first assistant director, rather than the normal route of runner followed by third and second assistant director, working on Channel 4 comedy shows and ITV's The Bill ("an unusual episode set at the Notting Hill Carnival") and production-managing several documentaries.

Continuity of work is always uncertain, says McCusker. "You are self-employed, and do a job on a contract basis for a few weeks or months. You just have to budget for the unemployed periods. It's all word of mouth; you work with people and hopefully they will want to work with you again. You network, make short films, possibly win some awards and then take advantage of whatever breaks may come from that."

Film crews rarely have more than one person doing the same thing, making it quite difficult to compare notes with people in the same role as yourself. For this reason McCusker joined the Production Managers Association, a group for experienced freelance production managers, and is chair of the association. In addition to running training workshops and quarterly networking events to enable members to get together and share experiences, it provides an "employment availability list", enabling producers and production companies to see which members are available for work, and to check their particular skills.

His big break came while waiting for an interview for a different job. He was on the floor in his brother's apartment when film-maker Dan Reed rang and asked if he would like to go to war. "He said, 'It's perfectly safe, we've got an armoured car. It's a very simple, straightforward job assuming we don't get any casualties.' Because I had lived in Belfast, they thought I would be fine in a war zone."

The offer led to McCusker being line producer on Reed's Channel 4 documentary The Valley, about the Kosovo Liberation Army in the Drenica valley. The beautiful and desolate film – an intimate portrait of ordinary people struggling to survive in the aftermath of a massacre – out in 1999, achieved great critical success, winning "shed loads of awards" and set the tone for his future career, encompassing thought-provoking and political films often set in the Middle East or Africa.

His projects include The Day Britain Stopped and Death of a President (both directed by Gabriel Range), the Battle for Haditha, an investigation into the massacre of 24 men, women and children in Iraq (directed by Nick Broomfield), and The Shooting of Thomas Hurndall, (directed by Rowan Joffe), the story of a British photography student who died after being shot in the head by an Israel Defence Forces sniper in the Gaza Strip in 2003. He is now tidying up some loose ends in post-production on a film about modern-day slavery in Sudan, again directed by Range and shot in the UK and Kenya's Rift Valley.

Given the political nature of his work, it's not surprising McCusker and the film crews he has worked with have received death threats, including one from al-Qaida. But he dismisses reports that The Hurt Locker's crew was shot at. "The Iraq border was hundreds of miles away," he says. "There was a sign saying 'Iraq', that was it. As a production manager you try not to put people in the line of fire."

Like many careers that appear glamorous from the outside, working in the film industry is hard graft with little in the way of glitter. Even with the success of The Hurt Locker, McCusker was not invited to the Oscars ceremony. That was only for nominees, so like everyone else he watched it on TV. So has his association with the film made a big difference to his career?

"Well I've signed up with an agent to promote me in the US. This will cover work making US films in Africa and the Middle East: I've done more films in Jordan than anybody."

But the reality is life remains uncertain. "I'm between jobs, not on anyone's payroll," he points out. "The fact is that the Hurt Locker was a small film which achieved fantastic success and in this business more than most success is very good to be associated with. I now have the challenge of capitalising on this. There are another four films in the offing that are trying to get finance and they need me to do things for them. Perhaps one will make it. It's a very risky business."

CV

Pay Co-producers on TV documentaries can earn up to £1,400 a week, on drama programmes from £1,500 to £1,800 a week, and on feature films from £2,000 a week. "If a film makes lots of money, I don't get anything back from that. I'm too low down the food chain."

Hours "People do 11 hours on set, but I do much longer, organising stuff. I also work long in advance of a film: for an eight-week shoot, I'll do 10 weeks of preparation."

Work-life balance Given the hours, none. Making films can make family life very difficult unless one or both partners compromise.

Best thing "Going to places you might not go very often and meeting people you wouldn't otherwise."

Worst thing "You simply sell your life to a film, so you don't get any time off. You work very long hours. When I was in Jordan for 14 months I didn't have a day off. You recover while you are unemployed."

Overtime

Donall's biggest disaster was when the entire negative for a £500,000 film, That Deadwood Feeling starring Dexter Fletcher, Angus Deayton and Jack Davenport, went missing. The film was subsequently released on DVD using a low-quality negative.

Donall is "absolutely against" the eating of popcorn in cinemas, and tends to go to private screenings and Bafta showings to avoid the added sound effects.

Donall still hasn't seen any of the Oscar statuettes for The Hurt Locker: "I'll get around to it."